1. Technical Field
The present disclosure relates to electrosurgical apparatuses, systems and methods. More particularly, the present disclosure is directed to electrosurgical generators configured to control energy output on a per arc basis. The generator detects aberrations within continuous or pulsed waveforms indicative of sudden changes in the current. In particular the generator monitors for deviations from the sinusoidal or pulsed sinusoidal current waveforms as compared to the voltage waveform.
2. Background of Related Art
Energy-based tissue treatment is well known in the art. Various types of energy (e.g., electrical, ultrasonic, microwave, cryogenic, heat, laser, etc.) are applied to tissue to achieve a desired result. Electrosurgery involves application of high radio frequency electrical current to a surgical site to cut, ablate, coagulate or seal tissue. In monopolar electrosurgery, an active electrode delivers radio frequency energy from the electrosurgical generator to the tissue and a return electrode carries the current back to the generator. In monopolar electrosurgery, the active electrode is typically part of the surgical instrument held by the surgeon and applied to the tissue to be treated. A patient return electrode is placed remotely from the active electrode to carry the current back to the generator.
Ablation is most commonly a monopolar procedure that is particularly useful in the field of cancer treatment, where one or more RF ablation needle electrodes (usually having elongated cylindrical geometry) are inserted into a living body and placed in the tumor region of an affected organ. A typical form of such needle electrodes incorporates an insulated sheath from which an exposed (uninsulated) tip extends. When an RF energy is provided between the return electrode and the inserted ablation electrode, RF current flows from the needle electrode through the body. Typically, the current density is very high near the tip of the needle electrode, which tends to heat and destroy surrounding issue.
In bipolar electrosurgery, one of the electrodes of the hand-held instrument functions as the active electrode and the other as the return electrode. The return electrode is placed in close proximity to the active electrode such that an electrical circuit is formed between the two electrodes (e.g., electrosurgical forceps). In this manner, the applied electrical current is limited to the body tissue positioned immediately adjacent the electrodes. When the electrodes are sufficiently separated from one another, the electrical circuit is open and thus inadvertent contact with body tissue with either of the separated electrodes does not cause current to flow.
During electrosurgical procedures, the magnitude and temporal characteristics of the voltage and current as supplied by the electrosurgical generator determine energy density pathways and tissue temperatures. This may be accomplished by keeping the total delivered power constant while varying other energy properties, such as voltage, current, etc. These configurations are not configured for detecting and controlling arcing conditions between the active electrode and tissue. It is particularly desirable to prevent the occurrence of uncontrolled electrical arcs and concomitant energy deposition on a half cycle or shorter time scale, in order to avoid inadvertent tissue damage and to achieve optimum conditions. Thus, there is a continual need for electrosurgical generators which are configured to sense tissue and energy properties to determine arcing conditions and control energy output based on these determinations.